The invention relates to a wood screw.
Wood screws comprise a threaded shank with a pointed tip at one end thereof and a head at the other end. The head has a recess for accepting a screwdriver tip.
Most wood screws have a conical head. Thus, when a wood screw is driven and the conical head begins to penetrate into a wooden plate, the turning resistance increases suddenly due to large friction. Therefore, a large turning torque is needed to drive the screw completely.
A power screwdriver or a torque wrench with a built-in torque limiter is often used to drive a wood screw into a wooden plate. In such a case, since the turning torque increases suddenly and sharply when the conical head begins to penetrate into the plate, the torque limiter may activate to stop the transmission of turning torque before the head is fully buried in the plate. If this happens, it is impossible to completely drive the screw into the plate. The screw head would remain above the plate surface.
When the conical head begins to penetrate into the plate, it is jammed into the narrow hole formed by the threads on the shank and acts like a wedge. Thus, even if the head is completely buried in the plate, the wooden plate tends to be cracked.
An object of the invention is to provide a wood screw that can be completely driven into a wooden plate with a small turning torque without forming a crack in the wooden plate.